CN115299169A

CN115299169A - Independent Sidelink (SL) Discontinuous Reception (DRX)

Info

Publication number: CN115299169A
Application number: CN202180022308.4A
Authority: CN
Inventors: L·丁; 厉隽怿; S·阿卡拉卡兰; J·H·刘; 张倩; 白天阳; K·文努戈帕尔; J·达姆尼亚诺维奇; 骆涛
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2020-03-26
Filing date: 2021-02-26
Publication date: 2022-11-04
Also published as: WO2021194693A1; US11758481B2; EP4128982A1; US20210306948A1

Abstract

A method of wireless communication by a sidelink UE (user equipment) comprising: a first signal is received at a beginning of a sidelink Discontinuous Reception (DRX) on duration as part of a Discontinuous Reception (DRX) wake-up procedure. The method further comprises the following steps: a response to the first signal is sent as part of the DRX wake-up procedure. The method further comprises the following steps: a timer is started after sending the response. The method further comprises the following steps: the sleep state is entered when a physical side uplink control channel (PSCCH) or a physical side uplink shared channel (pscsch) is not received before the timer expires.

Description

Independent Sidelink (SL) Discontinuous Reception (DRX)

Cross Reference to Related Applications

This application claims the benefit of U.S. patent application No. 17/153,097, entitled "apparatus and method for delivering information and receiving (DRX)" filed 20/1, 2021, which claims the benefit of U.S. provisional patent application No. 63/000,376, filed 26/3/2020, entitled "apparatus and method for delivering information and receiving (DRX)" filed SL, and the disclosure of which is expressly incorporated by reference in its entirety.

Technical Field

Aspects of the present disclosure relate generally to wireless communications, and more specifically to techniques and apparatus for a 5G New Radio (NR) independent Sidelink (SL) Discontinuous Reception (DRX) procedure for sidelink communications.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. A typical wireless communication system may employ multiple-access techniques capable of supporting communication with multiple users by sharing the available system resources. Examples of such multiple-access techniques include Code Division Multiple Access (CDMA) systems, time Division Multiple Access (TDMA) systems, frequency Division Multiple Access (FDMA) systems, orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access techniques have been employed in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate at the urban, national, regional, and even global levels. An example telecommunications standard is the fifth generation (5G) New Radio (NR). The 5G NR is part of a continuous mobile broadband evolution promulgated by the third generation partnership (3 GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with the internet of things (IoT)), and other requirements. The 5G NR comprises services associated with: enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable low latency communication (URLLC). Some aspects of the 5G NR may be based on fourth generation (4G) Long Term Evolution (LTE) standards. There is a need for further improvement of the 5G NR technology. These improvements may also be applicable to other multiple access techniques and telecommunications standards that employ these techniques.

The wireless communication system may include or provide support for various types of peer-to-peer communication systems, such as vehicle-related communication systems (e.g., vehicle-to-anything (V2X) communication systems). In some cases, vehicles may communicate directly with each other using device-to-device (D2D) communication over a D2D wireless link. As the demand for peer-to-peer communication (or D2D communication) increases, power saving becomes more and more important. Accordingly, there is a need to improve power savings during peer-to-peer wireless communications.

Disclosure of Invention

In one aspect of the disclosure, a method of wireless communication by a sidelink UE (user equipment) comprises: a first signal is received at a beginning of a sidelink DRX on duration as part of a Discontinuous Reception (DRX) wake-up procedure. The method further comprises the following steps: transmitting a response to the first signal as part of a DRX wakeup process. The method further comprises the following steps: a timer is started after sending the response. The method further comprises the following steps: entering a sleep state when a physical side uplink control channel (PSCCH)/physical side uplink shared channel (PSSCH) is not received before the timer expires.

In another aspect of the disclosure, a side-link UE (user equipment) for wireless communication includes a memory and at least one processor operably coupled to the memory. The memory and the at least one processor are configured to: a first signal is received at a beginning of a sidelink DRX on duration as part of a Discontinuous Reception (DRX) wake-up procedure. The UE also sends a response to the first signal as part of a DRX wake-up procedure. The UE starts a timer after sending the response. The UE enters a sleep state when the physical side uplink control channel (PSCCH)/physical side uplink shared channel (PSSCH) is not received before the timer expires.

In another aspect of the disclosure, a Sidelink (SL) UE includes: means for receiving a first signal at a beginning of a sidelink DRX on duration as part of a Discontinuous Reception (DRX) wake-up procedure. The SL UE further comprises: means for transmitting a response to the first signal as part of a DRX wake-up procedure. The SL UE further comprises: means for starting a timer after sending the response. The UE further comprises: means for entering a sleep state when a physical side uplink control channel (PSCCH)/physical side uplink shared channel (PSSCH) is not received before the timer expires.

Aspects include, in general, methods, apparatuses, systems, computer program products, non-transitory computer-readable media, user equipment, base stations, wireless communication devices, and processing systems substantially as described herein with reference to and as illustrated by the accompanying figures and description.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. The nature of the disclosed concepts (both their organization and method of operation), together with the associated advantages, will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description and is not intended as a definition of the limits of the claims.

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a diagram illustrating an example of a wireless communication system and an access network.

Fig. 2A, 2B, 2C, and 2D are diagrams illustrating examples of a first fifth generation (5G) New Radio (NR) frame, a Downlink (DL) channel within a 5G NR subframe, an Uplink (UL) channel within a second 5G NR frame, and a 5G NR subframe, respectively.

Fig. 3 is a diagram illustrating an example of a base station and a User Equipment (UE) in an access network.

Fig. 4 is a diagram illustrating an example of a vehicle-to-anything (V2X) system, according to aspects of the present disclosure.

Fig. 5 is a diagram illustrating a Discontinuous Reception (DRX) cycle, according to aspects of the present disclosure.

Fig. 6 is a diagram illustrating a DRX wake-up procedure in accordance with aspects of the present disclosure.

Fig. 7 is a diagram illustrating DRX cycles with various activities and timers, according to aspects of the present disclosure.

Fig. 8 is a diagram illustrating a DRX cycle with various activities and timers when a UE is transmitting to another UE, in accordance with aspects of the present disclosure.

Fig. 9 is a diagram illustrating a DRX cycle with various activities and timers when a UE is receiving from another UE, in accordance with aspects of the present disclosure.

Fig. 10A and 10B are diagrams illustrating a sidelink random access procedure according to aspects of the present disclosure.

Fig. 11 is a diagram illustrating an example process performed, for example, by a sidelink user equipment, in accordance with aspects of the present disclosure.

Detailed Description

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the present disclosure is intended to cover any aspect of the disclosed disclosure, whether implemented independently of or combined with any other aspect of the present disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth. Moreover, the scope of the present disclosure is intended to cover such an apparatus or method implemented with other structure, functionality, or structure and functionality in addition to or other than the various aspects of the present disclosure set forth herein. It should be understood that any aspect of the disclosed disclosure may be embodied by one or more elements of a claim.

Several aspects of a telecommunications system will now be presented with reference to various apparatus and techniques. These apparatus and techniques are described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, procedures, algorithms, etc. (collectively referred to as "elements"). These elements may be implemented using hardware, software, or a combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

It should be noted that although aspects may be described using terms commonly associated with 5G and beyond wireless technologies, aspects of the present disclosure may be applied in communication systems based on other generations, such as and including 3G and/or 4G technologies.

In a cellular communication network, wireless devices may typically communicate with each other via one or more network entities, such as a base station or a scheduling entity. Some networks may support device-to-device (D2D) communication, which enables discovery and communication with nearby devices using a direct link between the devices (e.g., without going through a base station, a relay, or another node). D2D communication may implement mesh networks and device-to-network relay functionality. Some examples of D2D technologies include Bluetooth pairing, wi-Fi direct, miracast, and LTE-D. D2D communication may also be referred to as point-to-point (P2P) or sidelink communication.

D2D communication may be implemented using licensed or unlicensed frequency bands. In addition, D2D communications may avoid the overhead involved in routing to and from the base station. Thus, D2D communication may improve throughput, reduce latency, and/or improve energy efficiency.

One type of D2D communication may include vehicle-to-anything (V2X) communication. V2X communication may help autonomous vehicles communicate with each other. For example, an autonomous vehicle may include a plurality of sensors (e.g., light detection and ranging (LiDAR), radar, cameras, etc.). In most cases, the sensor of the autonomous vehicle is a line of sight sensor. In contrast, V2X communication may allow autonomous vehicles to communicate with each other for non-line-of-sight situations.

To improve the correlation of the sidelink transmissions, the UEs may coordinate with each other to share resource information. That is, the first UE may identify the communication resource. The communication resources identified by the first UE may be referred to as sensing information. The first UE may send sensing information (e.g., the identified communication resources) to the second UE. The second UE may consider the sensing information in selecting resources for the sidelink transmission.

Aspects of the present disclosure present independent Sidelink (SL) Discontinuous Reception (DRX) procedures to conserve power for sidelink UEs. Here, the standalone SL DRX means that there is no Uu connection (connection with the base station) or a Uu DRX cycle (DRX cycle for base station communication). The present disclosure is valid when one UE is communicating with one or more UEs on a SL. The present disclosure is particularly applicable to scheduled mode 2 communications. Mode 2 communication is communication in which a base station does not assign resources. Instead, the UE autonomously selects resources from the resource pool.

Fig. 1 is a diagram illustrating an example of a wireless communication system and an access network 100. A wireless communication system, also referred to as a Wireless Wide Area Network (WWAN), includes a base station 102, a UE 104, an Evolved Packet Core (EPC) 160, and another core network 190 (e.g., a 5G core (5 GC)). Base station 102 may include macro cells (high power cellular base stations) and/or small cells (low power cellular base stations). The macro cell includes a base station. The small cells 102' include femtocells, picocells, and microcells.

A base station 102 configured for 4G LTE, collectively referred to as evolved Universal Mobile Telecommunications System (UMTS) terrestrial radio access network (E-UTRAN), may interface with the EPC 160 through a backhaul link 132 (e.g., S1 interface). A base station 102 configured for a 5G NR (collectively referred to as a next generation RAN (NG-RAN)) may interface with a core network 190 through a backhaul link 184. The base station 102 may perform one or more of the following functions, among others: transmission of user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio Access Network (RAN) sharing, multimedia Broadcast Multicast Service (MBMS), user and device tracking, RAN Information Management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (e.g., through the EPC 160 or the core network 190) over a backhaul link 134 (e.g., an X2 interface). The backhaul link 134 may be wired or wireless.

The base station 102 may be in wireless communication with the UE 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, a small cell 102 'may have a coverage area 110' that overlaps with the coverage areas 110 of one or more macro base stations 102. A network that includes both small cells and macro cells may be referred to as a heterogeneous network. The heterogeneous network may also include a home evolved node B (eNB) (HeNB), which may provide services to a restricted group known as a Closed Subscriber Group (CSG). The communication link 120 between the base station 102 and the UE 104 may include an Uplink (UL) (also referred to as a reverse link) transmission from the UE 104 to the base station 102 and/or a Downlink (DL) (also referred to as a forward link) transmission from the base station 102 to the UE 104. The communication link 120 may use multiple-input multiple-output (MIMO) antenna techniques including spatial multiplexing, beamforming, and/or transmit diversity. The communication link may be through one or more carriers. The base station 102/UE 104 may use a spectrum of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of yxmhz (x component carriers) for transmission in each direction. The carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than UL). The component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell), and the secondary component carrier may be referred to as a secondary cell (SCell).

Some UEs 104 may communicate with each other using a device-to-device (D2D) communication link 158. The D2D communication link 158 may use DL/UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a Physical Sidelink Broadcast Channel (PSBCH), a Physical Sidelink Discovery Channel (PSDCH), a physical sidelink shared channel (psch), and a Physical Sidelink Control Channel (PSCCH). The D2D communication may be through a variety of wireless D2D communication systems, such as FlashLinQ, wiMedia, bluetooth, zigBee (ZigBee), wi-Fi based on IEEE 802.11 standards, LTE, or NR.

The wireless communication system may also include a Wi-Fi Access Point (AP) 150 that communicates with a Wi-Fi Station (STA) 152 via a communication link 154 in a 5GHz unlicensed spectrum. When communicating in the unlicensed spectrum, STA 152/AP 150 may perform a Clear Channel Assessment (CCA) prior to the communication in order to determine whether a channel is available.

The small cell 102' may operate in licensed and/or unlicensed spectrum. When operating in unlicensed spectrum, the small cell 102' may employ NR and use the same 5GHz unlicensed spectrum as used by the Wi-Fi AP 150. A small cell 102' employing NR in unlicensed spectrum may improve coverage and/or increase capacity of an access network.

The base station 102, whether a small cell 102' or a large cell (e.g., a macro base station), may include an eNB, a gnnodeb (gNB), or another type of base station. Some base stations, such as the gNB 180, may operate in a conventional below 6GHz spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies to communicate with the UE 104. When gNB 180 operates in a mmW or near mmW frequency, gNB 180 may be referred to as a mmW base station. Extremely High Frequency (EHF) is a portion of the Radio Frequency (RF) in the electromagnetic spectrum. The EHF has a range of 30GHz to 300GHz, and a wavelength between 1 millimeter and 10 millimeters. The radio waves in this frequency band may be referred to as millimeter waves. Near mmW can be extended down to a frequency of 3GHz, which has a wavelength of 100 mm. The ultra-high frequency (SHF) band extends between 3GHz and 30GHz, also known as centimeter waves. Communications using the mmW/near mmW radio frequency band (e.g., 3GHz-300 GHz) have extremely high path loss and short range. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for extremely high path loss and short range.

The base station 180 may transmit a beamformed signal to the UE 104 in one or more transmit directions 182'. The UE 104 may receive beamformed signals from the base station 180 in one or more receive directions 182 ". The UE 104 may also transmit beamforming signals to the base station 180 in one or more transmit directions. The base station 180 may receive beamformed signals from the UEs 104 in one or more receive directions. The base station 180/UE 104 may perform beam training to determine the best receive and transmit directions for each of the base station 180/UE 104. The transmit direction and the receive direction for the base station 180 may or may not be the same. The transmit direction and the receive direction for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a serving gateway 166, a Multimedia Broadcast Multicast Service (MBMS) gateway 168, a broadcast multicast service center (BM-SC) 170, and a Packet Data Network (PDN) gateway 172.MME 162 may communicate with Home Subscriber Server (HSS) 174. MME 162 is a control node that handles signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transported through the serving gateway 166, which is itself connected to the PDN gateway 172. The PDN gateway 172 provides UE IP address allocation as well as other functions. The PDN gateway 172 and BM-SC 170 are connected to IP services 176.IP services 176 may include the internet, intranets, IP Multimedia Subsystem (IMS), PS streaming services, and/or other IP services. The BM-SC 170 may provide functions for MBMS user service setup and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and may be used to schedule MBMS transmissions. The MBMS gateway 168 may be used to distribute MBMS traffic to base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS-related charging information.

The core network 190 may include an access and mobility management function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF192 may communicate with a unified data management Unit (UDM) 196. The AMF192 is a control node that handles signaling between the UE 104 and the core network 190. In general, the AMF192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transported through the UPF 195. The UPF 195 provides UE IP address assignment as well as other functions. The UPF 195 is connected to the IP service 197. The IP services 197 may include the internet, intranets, IP Multimedia Subsystem (IMS), PS streaming services, and/or other IP services.

Base station 102 may also be referred to as a gNB, a node B, an evolved node B (eNB), an access point, a base transceiver station, a wireless base station, a wireless transceiver, a transceiver function, a Basic Service Set (BSS), an Extended Service Set (ESS), a Transmit Receive Point (TRP), or some other suitable terminology. The base station 102 provides an access point to the EPC 160 or the core network 190 for the UE 104. Examples of UEs 104 include cellular phones, smart phones, session Initiation Protocol (SIP) phones, laptops, personal Digital Assistants (PDAs), satellite radios, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablets, smart devices, wearable devices, vehicles, electricity meters, gas pumps, large or small kitchen appliances, healthcare devices, implants, sensors/actuators, displays, or any other similar functioning device. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meters, gas pumps, ovens, vehicles, cardiac monitors, etc.). The UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handheld device, user agent, mobile client, or some other suitable terminology.

Although the following description may focus on 5G NR, aspects of the disclosure may be applicable to other similar fields, such as LTE, LTE-a, CDMA, GSM, and other wireless technologies.

Fig. 2A is a diagram 200 illustrating an example of a first sub-frame within a 5G/NR frame structure. Fig. 2B is a diagram 230 illustrating an example of DL channels within a 5G NR subframe. Fig. 2C is a diagram 250 illustrating an example of a second subframe within a 5G NR frame structure. Fig. 2D is a diagram 280 illustrating an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency division multiplexing (FDD) in which a subframe within the subcarrier set is dedicated to either DL or UL for a particular subcarrier set (carrier system bandwidth), or the 5G/NR frame structure may be time division multiplexing (TDD) in which a subframe within the subcarrier set is dedicated to both DL and UL for a particular subcarrier set (carrier system bandwidth). In the example provided in fig. 2A, 2C, it is assumed that the 5G NR frame structure is TDD, where subframe 4 is configured with slot format 28 (where DL is dominant), where D is DL, U is UL, and X is flexibly used between DL/UL, and subframe 3 is configured with slot format 34 (where UL is dominant). Although

subframes

3,4 are shown as having slot formats 34, 28, respectively, any particular subframe may be configured with any of a variety of available slot formats 0-61. Slot formats 0, 1 are full DL, full UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with a slot format (dynamically configured through DL Control Information (DCI) or semi-statically/statically configured through Radio Resource Control (RRC) signaling) through a received Slot Format Indicator (SFI). It should be noted that the following description is also applicable to the 5G NR frame structure as TDD.

Other wireless communication technologies may have different frame structures and/or different channels. A frame (e.g., 10 ms) may be divided into subframes (1 ms) of the same size. Each subframe may include one or more slots. A subframe may also include a minislot, which may include 7, 4, or 2 symbols. Each slot may comprise 7 or 14 symbols, depending on the slot configuration. Each slot may include 14 symbols for

slot configuration

0 and 7 symbols for slot configuration 1. The symbols on the DL may be Cyclic Prefix (CP) OFDM (CP-OFDM) symbols. The symbols on the UL may be CP-OFDM symbols (for high throughput scenarios) or Discrete Fourier Transform (DFT) spread OFDM (DFT-S-OFDM) symbols (also known as single carrier frequency division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to single stream transmission). The number of slots within a subframe is based on the slot configuration and the numbering scheme. For slot configuration 0, different numerologies μ 0 to 5 allow 1, 2, 4, 8, 16 and 32 slots per sub-frame, respectively. For slot configuration 1, different numerologies 0 to 2 allow 2, 4 and 8 slots per sub-frame, respectively. Thus, for slot configuration 0 and numerology μ, there are 14 symbols/slot and 2 μ slots/subframe. The subcarrier spacing and symbol length/duration are functions of the digital scheme. The subcarrier spacing may be equal to 2^ mu x 15kKz, where mu is digital scheme 0-5. As such, digital scheme μ =0 has a subcarrier spacing of 15kHz, and digital scheme μ =5 has a subcarrier spacing of 480 kHz. The symbol length/duration is inversely proportional to the subcarrier spacing. Fig. 2A-2D provide examples of a slot configuration 0 with 14 symbols per slot and a numerical scheme μ =0 with 1 slot per subframe. The subcarrier spacing is 15kHz and the symbol duration is approximately 66.7 mus.

The resource grid may represent a frame structure. Each slot may include a Resource Block (RB) (also referred to as a Physical RB (PRB)) that extends 12 consecutive subcarriers. The resource grid may be divided into a plurality of Resource Elements (REs). The number of bits carried by each RE may depend on the modulation scheme.

As shown in fig. 2A, some of the REs may carry reference (pilot) signals (RSs) for the UE. The RSs may include demodulated RS (DM-RS) used for channel estimation at the UE (indicated as Rx for one particular configuration (where 100x is a port number), but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS). The RSs may also include a beam measurement RS (BRS), a Beam Refinement RS (BRRS), and a phase tracking RS (PT-RS).

Fig. 2B shows examples of various DL channels within a subframe of a frame. The Physical Downlink Control Channel (PDCCH) carries DCI in one or more Control Channel Elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. The Primary Synchronization Signal (PSS) may be within symbol 2 of a particular subframe of the frame. The PSS is used by the UE 104 to determine subframe/symbol timing and physical layer identity. A Secondary Synchronization Signal (SSS) may be within symbol 4 of a particular subframe of a frame. The SSS is used by the UE to determine the physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE may determine a Physical Cell Identifier (PCI). Based on the PCI, the UE may determine the location of the aforementioned DM-RS. A Physical Broadcast Channel (PBCH) carrying a Master Information Block (MIB) may be logically grouped with a PSS and an SSS to form a Synchronization Signal (SS)/PBCH block. The MIB provides the number of RBs and the System Frame Number (SFN) in the system bandwidth. The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information such as System Information Blocks (SIBs) that are not transmitted through the PBCH, and a paging message.

As shown in fig. 2C, some of the REs carry DM-RS for channel estimation at the base station (which is indicated as R for one particular configuration, but other DM-RS configurations are possible). The UE may transmit DM-RS for a Physical Uplink Control Channel (PUCCH) and DM-RS for a Physical Uplink Shared Channel (PUSCH). The PUSCH DM-RS may be transmitted in the first or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether the short PUCCH or the long PUCCH is transmitted and depending on the particular PUCCH format used. Although not shown, the UE may transmit a Sounding Reference Signal (SRS). SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

Fig. 2D shows examples of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries Uplink Control Information (UCI) such as scheduling request, channel Quality Indicator (CQI), precoding Matrix Indicator (PMI), rank Indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgement/negative acknowledgement (ACK/NACK) feedback. The PUSCH carries data, and may additionally be used to carry Buffer Status Reports (BSRs), power Headroom Reports (PHR), and/or UCI.

Fig. 3 is a block diagram of a base station 310 in an access network in communication with a UE 350. In the DL, IP packets from EPC 160 may be provided to controller/processor 375. Controller/processor 375 implements layer 3 and layer 2 functions. Layer 3 includes a Radio Resource Control (RRC) layer, and layer 2 includes a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Medium Access Control (MAC) layer. The controller/processor 375 provides: RRC layer functions associated with: broadcast of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-Radio Access Technology (RAT) mobility, and measurement configuration for UE measurement reporting; a PDCP layer function associated with: header compression/decompression, security (encryption, decryption, integrity protection, integrity verification) and handover support functions; RLC layer functions associated with: delivery of upper layer Packet Data Units (PDUs), error correction by ARQ, concatenation, segmentation and reassembly of RLC Service Data Units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functions associated with: mapping between logical channels and transport channels, multiplexing of MAC SDUs onto Transport Blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, priority handling and logical channel prioritization.

The Transmit (TX) processor 316 and the Receive (RX) processor 370 perform layer 1 functions associated with various signal processing functions. Layer 1, which includes the Physical (PHY) layer, may include error detection for the transport channel, forward Error Correction (FEC) encoding/decoding for the transport channel, interleaving, rate matching, mapping onto the physical channel, modulation/demodulation for the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., binary Phase Shift Keying (BPSK), quadrature Phase Shift Keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel that carries a time-domain OFDM symbol stream. The OFDM streams are spatially precoded to produce a plurality of spatial streams. The channel estimates from channel estimator 374 may be used to determine coding and modulation schemes and for spatial processing. The channel estimates may be derived from reference signals and/or channel condition feedback transmitted by the UE 350. Each spatial stream is then provided to a different antenna 320 via a separate transmitter 318 TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the UE350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to a Receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functions associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE350, the RX processor 356 may combine them into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on channel estimates computed by channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to a controller/processor 359, which controller/processor 359 implements layer 3 and layer 2 functions.

The controller/processor 359 can be associated with memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression and control signal processing to recover IP packets from EPC 160. The controller/processor 359 is also responsible for error detection using ACK and/or NACK protocols to support HARQ operations.

Similar to the functionality described in connection with the DL transmission by base station 310, controller/processor 359 provides: RRC layer functionality associated with: system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; a PDCP layer function associated with: header compression/decompression and security (encryption, decryption, integrity protection, integrity verification); an RLC layer function associated with: transmission of upper layer PDUs, error correction by ARQ, concatenation, segmentation and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-sequencing of RLC data PDUs; and MAC layer functions associated with: mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, priority handling and logical channel prioritization.

Channel estimates, derived by a channel estimator 358 from a reference signal or feedback transmitted by base station 310, may be used by TX processor 368 to select an appropriate coding and modulation scheme, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354 TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

At the base station 310, the UL transmissions are processed in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its corresponding antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to an RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from controller/processor 375 may be provided to EPC 160. The controller/processor 375 is also responsible for supporting HARQ operations using error detection for ACK and/or NACK protocols.

In some aspects, the

UE

104, 350 may include: means for receiving, means for transmitting, means for starting, means for entering a sleep state, and means for remaining awake. Such means may include one or more components of the

UE

104, 350 described in connection with fig. 1 and 3.

Fig. 4 is a diagram of a device-to-device (D2D) communication system 400, according to aspects of the present disclosure. For example, the D2D communication system 400 may include V2X communication (e.g., the first UE450 communicates with the second UE 451). In some aspects, the first UE450 and/or the second UE451 may be configured to communicate in a licensed radio frequency spectrum and/or a shared radio frequency spectrum. The shared radio frequency spectrum may be unlicensed, and thus a variety of different technologies may communicate using the shared radio frequency spectrum, including New Radio (NR), LTE advanced, licensed Assisted Access (LAA), dedicated Short Range Communication (DSRC), muLTEFire, 4G, and so on. The above list of techniques should be considered illustrative and not meant to be exhaustive.

The D2D communication system 400 may use NR radio access technology. Of course, other radio access technologies may be used, such as LTE radio access technology. In D2D communications, e.g., V2X communications or vehicle-to-vehicle (V2V) communications, the

UEs

450, 451 may be on different Mobile Network Operator (MNO) networks. Each of these networks may operate in its own radio frequency spectrum. For example, the air interface (e.g., uu interface) to the first UE450 may be on one or more frequency bands different from the air interface of the second UE 451. The first UE450 and the second UE451 may communicate via a sidelink component carrier (e.g., via a PC5 interface). In some examples, the base station may schedule sidelink communications between or among the

UEs

450, 451 in a licensed radio frequency spectrum and/or a shared radio frequency spectrum (e.g., a 5GHz radio frequency spectrum band). This is referred to as scheduled mode 1 communication.

The shared radio frequency spectrum may be unlicensed, and thus different technologies may communicate using the shared radio frequency spectrum. In some aspects, D2D communications (e.g., sidelink communications) between or among the

UEs

450, 451 are not scheduled by the base station. This is referred to as scheduling mode 2 communication, where the UE itself schedules resources autonomously.

The D2D communication system 400 may also include a third UE 452. For example, the third UE452 may operate on the first network 410 (e.g., of the first MNO) or another network. The third UE452 may be in D2D communication with the first UE450 and/or the second UE 451. The first base station 420 (e.g., the gNB) may communicate with the third UE452 via a Downlink (DL) carrier 432 and/or an Uplink (UL) carrier 442. DL communications may use various DL resources (e.g., DL subframes (fig. 2A) and/or DL channels (fig. 2B)). UL communications may be performed using various UL resources, e.g., UL subframes (fig. 2C) and UL channels (fig. 2D), via UL carrier 442.

For example, as described in fig. 1-3, the first network 410 operates in a first spectrum and includes a first base station 420 (e.g., a gNB) that communicates with at least a first UE 450. A first base station 420 (e.g., a gNB) may communicate with a first UE450 via a DL carrier 430 and/or an UL carrier 440. DL communications may use various DL resources (e.g., DL subframes (fig. 2A) and/or DL channels (fig. 2B)). UL communication may be performed using various UL resources, e.g., UL subframes (fig. 2C) and UL channels (fig. 2D), via UL carrier 440.

In some aspects, the second UE451 may be on a different network than the first UE 450. In some aspects, the second UE451 may be on the second network 411 (e.g., of the second MNO). For example, as described in fig. 1-3, the second network 411 may operate in a second frequency spectrum (e.g., a second frequency spectrum different from the first frequency spectrum) and may include a second base station 421 (e.g., a gNB) in communication with a second UE 451.

The second base station 421 may communicate with the second UE451 via a DL carrier 431 and an UL carrier 441. DL communications are performed using various DL resources, e.g., DL subframes (fig. 2A) and/or DL channels (fig. 2B), via DL carriers 431. UL communication is performed using various UL resources, e.g., UL subframes (fig. 2C) and/or UL channels (fig. 2D), via UL carrier 441.

In the scheduling mode 1 system, the first base station 420 and/or the second base station 421 allocate resources for device-to-device (D2D) communication (e.g., V2X communication and/or V2V communication) to UEs. For example, a resource may be a UL resource pool that is both orthogonal (e.g., one or more FDM channels) and non-orthogonal (e.g., code Division Multiplexing (CDM)/Resource Spreading Multiple Access (RSMA) in each channel). The first base station 420 and/or the second base station 421 may configure resources via PDCCH (e.g., faster method) or RRC (e.g., slower method).

D2D communications (e.g., V2X communications and/or V2V communications) may be performed via one or more

sidelink carriers

470, 480. The one or more

sidelink carriers

470, 480 may include one or more channels, such as, for example, a Physical Sidelink Broadcast Channel (PSBCH), a Physical Sidelink Discovery Channel (PSDCH), a Physical Sidelink Shared Channel (PSSCH), and a Physical Sidelink Control Channel (PSCCH).

In some examples, the

sidelink carriers

470, 480 may operate using a PC5 interface. The first UE450 may transmit to one or more (e.g., multiple) devices (including to the second UE 451) via the first sidelink carrier 470. The second UE451 may transmit to one or more (e.g., multiple) devices (including to the first UE 450) via the second sidelink carrier 480.

In some aspects, UL carrier 440 and first sidelink carrier 470 may be aggregated to increase bandwidth. In some aspects, the first sidelink carrier 470 and/or the second sidelink carrier 480 may share a first spectrum (with the first network 410) and/or a second spectrum (with the second network 411). In some aspects, the

sidelink carriers

470, 480 may operate in an unlicensed/shared radio frequency spectrum.

In some aspects, sidelink communications over a sidelink carrier may occur between the first UE450 and the second UE 451. In an aspect, the first UE450 may perform sidelink communications with one or more (e.g., a plurality) of devices, including the second device 451, via a first sidelink carrier 470. For example, the first UE450 may send a broadcast transmission to multiple devices (e.g., the second UE451 and the third UE 452) via the first sidelink carrier 470. The second UE451 (e.g., among other UEs) may receive such a broadcast transmission. Additionally or alternatively, the first UE450 may send a multicast transmission to a plurality of devices (e.g., the second UE451 and the third UE 452) via the first sidelink carrier 470. The second UE451 and/or the third UE452 (e.g., among other UEs) may receive such a multicast transmission. Multicast transmissions may be connectionless or connection-oriented. Multicast transmission may also be referred to as multicast transmission.

Further, the first UE450 may send a unicast transmission to a device, such as the second UE451, via the first sidelink carrier 470. The second UE451 (e.g., among other UEs) may receive such a unicast transmission. Additionally or alternatively, the second UE451 can perform sidelink communications with one or more (e.g., multiple) devices, including the first UE450, via a second sidelink carrier 480. For example, the second UE451 may send a broadcast transmission to multiple devices via the second sidelink carrier 480. The first UE450 (e.g., among other UEs) may receive such a broadcast transmission.

In another example, the second UE451 may send a multicast transmission to multiple devices (e.g., the first UE450 and the third UE 452) via the second sidelink carrier 480. The first UE450 and/or the third UE452 (e.g., among other UEs) may receive such a multicast transmission. Further, the second UE451 may send unicast transmissions to devices such as the first UE450 via the second sidelink carrier 480. The first UE450 (e.g., among other UEs) may receive such unicast transmissions. The third UE452 may communicate in a similar manner.

In some aspects, for example, such sidelink communications between the first UE450 and the second UE451 over a sidelink carrier may occur without requiring an MNO to allocate resources (e.g., resource Blocks (RBs), slots, bands, and/or one or more portions of a channel associated with the sidelink carriers 470, 480) for such communications and/or without scheduling such communications. The sidelink communications may include traffic communications (e.g., data communications, control communications, paging communications, and/or system information communications). Further, the sidelink communications may include sidelink feedback communications associated with the traffic communications (e.g., transmission of feedback information for previously received traffic communications). The sidelink communications may employ at least one sidelink communications structure having at least one feedback symbol. The feedback symbols of the sidelink communication structure may be allocated for any sidelink feedback information that may be transmitted in a device-to-device (D2D) communication system 400 between devices (e.g., the first UE450, the second UE451, and/or the third UE 452).

In a Discontinuous Reception (DRX) mode of operation, the UE may enter a low power ("sleep") mode (which may also be referred to as a low power state) for a certain period of time (referred to as a DRX off period, phase, or duration) and wake up again during a DRX on period to check if there is any data to receive. The cycle of sleep and awake (DRX on and DRX off) periods repeats over time, allowing the UE to save power while maintaining the connection.

Fig. 5 shows an example DRX configuration 500 for a UE. As shown, the DRX configuration 500 may include DRX on

periods

502, 504. As described above, the DRX on period is repeated every DRX cycle 506. For example, DRX on period 502 is during DRX cycle 506. The UE wakes up during DRX on

periods

502, 504 to monitor for signaling that may be received and is in a low power state (e.g., sleep mode) at other times.

In some cases, multiple UEs in Sidelink (SL) communication may be configured with DRX. In some cases, the wake-up procedure may include beam scanning to facilitate communication between SL UEs. A UE transmitting a signal for beam scanning may be referred to as a Transmission (TX) UE, and a UE receiving a signal may be referred to as a Reception (RX) UE. For example, the RX UE may receive "i want to send" signaling (IWTS) 510 from the TX UE at the beginning of DRX on period 504, indicating that the TX UE has data to send. IWTS signaling 510 may also be used for beam management.

For the Uu link, the UE communicates with a Base Station (BS) and has one DRX setting (e.g., DRX setting with the base station). However, for SL communication, a UE may communicate with multiple UEs and may have multiple DRX settings (e.g., one DRX setting for each UE pair). According to the present disclosure, DRX on durations of UEs in SL communication are aligned.

In some aspects, DRX on periods may be aligned on different TX UEs in a time orthogonal manner. For a given RX UE, there may be only one TX UE in one DRX on phase, and beam management/scanning may be performed independently for different TX UEs (e.g., beam scanning may be performed for one UE pair at a time). This may be similar to beam management on the Uu link. However, this option for SL communication is expensive from a power consumption and processing power perspective, as there may be multiple SL UEs communicating with one. Furthermore, the likelihood of a TX UE contacting an RX UE during any given DRX on phase is relatively low. Thus, according to the present disclosure, it is assumed that one DRX setting for an RX UE (e.g., UE 0) is the same for all TX UEs.

Aspects of the present disclosure include a stand-alone SL DRX procedure to conserve UE power. Here, the independent SL DRX means that there is no Uu connection or Uu DRX. The present disclosure is valid when one UE (e.g., UE 0) communicates with one or more UEs over a SL. The present disclosure is particularly applicable to scheduled mode 2 communications. Mode 2 communication is communication in which a base station does not assign resources. Instead, the UE autonomously selects resources from the resource pool.

At the beginning of the DRX on duration, a DRX wake-up procedure occurs between the RX UE (e.g., UE 0) and the TX UE. For an FR2 (frequency range two millimeter wave) scenario, the wake-up process may include beam training or some other form of initialization that occurs for beam alignment between a TX UE (e.g., UE 1) and an RX UE (e.g., UE 0). For the FR1 (frequency range one-below 6 GHz) scenario, there is no beam sweep.

Fig. 6 is a diagram illustrating a DRX wake-up procedure according to aspects of the present disclosure. As mentioned above with respect to fig. 5 and shown in more detail in fig. 6, if a TX UE (e.g., UE 1) has data to send, the TX UE sends a "i want to send" (IWTS) signal at time t 1. The RX UE (e.g., UE 0) responds with an "i hear you" signal at time t 2. At time t3, the RX UE (e.g., UE 0) starts a timer and waits to receive data from the TX UE (e.g., UE 1). For example, an RX UE (e.g., UE 0) waits for a TX UE (e.g., UE 1) to transmit a first PSCCH/PSCCH at time t4, as described in more detail in U.S. patent application No. 62/983,286 entitled "Beam tracking for SL Configured with Discrete Reception (DRX)" filed on 28.2.2020, the disclosure of which is expressly incorporated herein in its entirety by reference.

Fig. 7 is a diagram illustrating DRX cycles with various activities and timers, in accordance with aspects of the present disclosure. The UE (e.g., UE 0) operates according to DRX settings 710 including a DRX on state and a DRX off state. As shown in fig. 7, the UE is active in the DRX wake-up phase during the sidelink DRX on duration. In case 1, if the physical sidelink channel (e.g., first PSCCH/PSCCH) is received before the timer of fig. 6 times out, the RX UE (e.g., UE 0) starts a sidelink inactivity timer at time t 1. After the timer in fig. 6 expires and the first physical sidelink channel is not received (e.g., when the TX UE (UE 1) has no data to send), the RX UE (e.g., UE 0) may sleep (e.g., enter DRX inactive state) as shown in fig. 7 at time t2 (case 2). In other words, if a timeout occurs and no physical sidelink channel is received, the RX UE goes to sleep if no ongoing timer requires the RX UE (e.g., UE 0) to be in DRX active state.

A new Sidelink (SL) timer will now be discussed in accordance with the present disclosure. A sidelink open duration Timer (SL drx-onDurationTimer), a sidelink inactivity Timer (SL drx-inactivity Timer-TX/SL drx-inactivity Timer-RX) for the transmitter and the receiver, a sidelink HARQ Timer (SL drx-HARQ-RTT-Timer-TX/SL drx-HARQ-RTT-Timer-RX) for the transmitter and the receiver, and a sidelink retransmission Timer (SL drx-retransmission Timer-TX/SL drx-retransmission-RX) for the transmitter and the receiver are introduced.

According to aspects of the present disclosure, the time position (e.g., offset and duration) of the SL drx-onDurationTimer takes into account the pre-configured PSCCH/PSCCH resource settings. In other words, the PSCCH/PSCCH resource should coincide with each drx-onDuration.

In another aspect of the disclosure, the SL drx-onDurationTimer, SL drx-inactivytimeter-TX/RX, and SL drx-retransmission timer-TX/RX are pre-configured. In particular, their duration is preconfigured.

In yet another aspect, the minimum duration of SL drx-HARQ-RTT-Timer-TX/RX is pre-configured. The actual timer duration is dynamically adjusted so that PSCCH/PSCCH resources are present during the input duration of SL drx-retransmission timer-TX/RX.

The duration of each of the above timers (minimum of SL drx-onDurationTimer, SL drx-InactivityTimer-TX/RX, SL drx-retransmission Timer-TX/RX, and SL drx-HARQ-RTT-Timer-TX/RX) may be preconfigured for each link (e.g., UE1, UE2, etc.) or each link type (e.g., type = unicast versus multicast, sidelink, or Uu), each traffic type (e.g., voice or data), or each UE (e.g., for the same sidelink as an RX UE (e.g., UE 0)).

When to start each timer is similar to that defined for the Uu case, except that for sidelink communications the grant is via the PSCCH. In other words, the sidelink DRX on duration timer is started after DRX-SlotOffset from the beginning of a subframe, where the subframe is such that for long DRX cycles, [ (subframe number (SFN) × 10) + subframe number ] mod (DRX-LongCycle) = DRX-StartOffset, and for short DRX cycles (if configured), [ (SFN × 10) + subframe number ] mod (DRX-ShortCycle) = (DRX-StartOffset) mod (DRX-ShortCycle). The time positions of the sidelink DRX on duration timer are DRX-StartOffset and DRX on duration timer. A sidelink inactivity timer TX is started at the transmission of psch/PSCCH; and a sidelink inactivity timer RX is started at the reception of the psch/PSCCH. A sidelink DRX HARQ Round Trip Time (RTT) timer TX is started at the transmission of PSSCH/PSCCH; and the sidelink DRX HARQ RTT timer RX is started at the transmission of a Negative Acknowledgement (NACK) on the received psch/PSCCH. A sidelink DRX retransmission timer TX is started when the sidelink DRX HARQ RTT timer TX expires; and the sidelink DRX retransmission timer RX is started when the sidelink DRX HARQ RTT timer RX expires.

An RX UE (e.g., UE 0) may choose to sleep during L drx-onDurationTimer, SL drx-inactivity timer, and SL drx-retransmission timer if there are no preconfigured PSCCH/PSCCH resources for the duration of these timers. The sidelink DRX cycle configuration (e.g., cycle start-offset, DRX-on duration, DRX-cycle length) may be the same as in the Uu case. In other words, the configuration of the long DRX cycle and optionally the configuration of the short DRX cycle may comply with the Uu specification.

Fig. 8 is a diagram illustrating a DRX cycle with various activities and timers when a UE is transmitting to another UE, in accordance with aspects of the present disclosure. The UE (e.g., UE 0) operates according to DRX settings 810 including a DRX on state and a DRX off state. Referring to fig. 8, various activities and timers will now be discussed for the case where UE0 transmits a physical side uplink channel (e.g., PSCCH/PSCCH) to another UE. After a UE (e.g., UE 0) receives a first psch/PSCCH from another UE (e.g., UE 1), an inactivity timer starts at time t1, similar to that discussed with reference to fig. 7. In this case (case a), the UE (UE 0) decides to transmit data. Thus, UE0 allocates resources and transmits PSCCH/PSCCH, which restarts the inactivity timer TX at time t 2. At the moment the inactivity timer TX restarts (when PSCCH/PSCCH is transmitted), SL drx-HARQ-RTT-timer-TX starts as well. When the inactivity timer expires at time t3, UE0 sleeps. After the expiration of SL drx-HARQ-RTT-timer-TX, SL drx-retransmission timer-TX starts and UE0 enters the active state at time t 4. Once SL drx retransmission timer TX expires without UE0 receiving a retransmission, UE0 returns to sleep mode at time t 5. At time t6, the UE wakes up according to the DRX setting.

Fig. 9 is a diagram illustrating a DRX cycle with various activities and timers when a UE is receiving from another UE, in accordance with aspects of the present disclosure. The UE (e.g., UE 0) operates according to DRX settings 910 that include a DRX on state and a DRX off state. Referring to fig. 9, various activities and timers will now be discussed for the case where a UE receives a physical side uplink channel (e.g., PSCCH/PSCCH) from another UE. After a UE (e.g., UE 0) receives a first psch/PSCCH from another UE (e.g., UE 1), an inactivity timer starts at time t1, similar to that discussed with reference to fig. 7. In this case (case B), the UE receives the psch/PSCCH from another UE (e.g., UE 1) and restarts the inactivity timer at time t2 accordingly. When nothing is received, UE0 sends a Negative Acknowledgement (NACK) at time t 3. UE0 sends a negative acknowledgement since the PSSCH is not received from another UE (e.g., UE 1). UE0 starts SL drx HARQ RTT timer RX and then sleeps at time t 4. When the inactivity timer expires, UE0 sleeps until SL drx-HARQ-RTT-timer-RX expires at time t 5. After the expiration of the SL drx-HARQ-RTT-timer-RX timer at time t5, the SL drx-retransmission timer-RX is started and UE0 wakes up to listen for the retransmission. Once SL drx retransmission timer RX expires without UE0 receiving a retransmission, UE0 enters sleep mode at time t 6. At time t7, the UE wakes up according to the DRX setting.

Random access procedures for sidelink communications are also contemplated, according to aspects of the present disclosure. According to this aspect, the UE remains awake throughout the random access procedure. More specifically, the UE remains awake until the final message is sent or received. The final message may be message-2 or message-3, depending on the SL random access design. Details of the Sidelink Random Access procedure may be found in U.S. provisional patent application No. 62/993,460, entitled "Techniques for Performing Random Access Procedures in Sidelink Wireless Communications," filed 3/23/2020, the disclosure of which is expressly incorporated herein in its entirety by reference.

Fig. 10A and 10B are diagrams illustrating a sidelink random access procedure according to aspects of the present disclosure. Referring to fig. 10A, a first type of sidelink random access procedure is shown, wherein the final message is message-2 (msg 2). In fig. 10A, UE0 may be UE1 or UE2. According to the process shown in FIG. 10A, UE1 transmits message-0 (msg 0) at time t1, and UE2 responds with message-one (msg 1) at time t 2. The power ramp up occurs at UE2 at time t3 until message-two (msg 2) is received at time t 4. The sending UE (UE 1) may go to sleep after sending message-2 at time t4, and the receiving UE may go to sleep after receiving message-2 at time t 4.

FIG. 10B shows the same process as described with respect to FIG. 10A for times t1-t 4. At time t5, UE1 performs retransmission of message-2 until message-3 arrives at time t 6. The sending UE (e.g., UE 2) may go to sleep after sending message-3 at time t 6. In this case, the receiving UE may go to sleep after receiving message-3 at time t 6. In fig. 10B, UE0 may be UE1 or UE2.

As noted above, fig. 5-10B are provided as examples. Other examples may differ from those described with respect to fig. 5-10B.

Fig. 11 is a diagram illustrating an example process 1100 performed, for example, by a sidelink UE (user equipment), in accordance with various aspects of the present disclosure. The example process 1100 is an example of independent Sidelink (SL) Discontinuous Reception (DRX).

As shown in fig. 11, in some aspects, process 1100 may include: as part of a Discontinuous Reception (DRX) wake-up procedure, a first signal is received at the beginning of a sidelink Discontinuous Reception (DRX) on duration (block 1102). For example, the UE may receive the first signal (e.g., using antennas 352, RX 354, RX processor 356, controller processor 359, memory 360, etc.).

As shown in fig. 11, in some aspects, process 1100 may include: a response to the first signal is sent as part of the DRX wake-up procedure (block 1104). For example, the UE (e.g., using antenna 352, TX 354, TX processor 368, controller processor 359, memory 360, etc.) may transmit a response.

As shown in fig. 11, in some aspects, process 1100 may include: a timer is started after sending the response (block 1106). For example, the UE (e.g., using controller processor 359, memory 360, etc.) may start a timer.

As shown in fig. 11, in some aspects, process 1100 may include: the sleep state is entered when the physical side uplink control channel (PSCCH) or the physical side uplink shared channel (PSCCH) is not received before the timer expires (block 1108). For example, the UE may enter a sleep state (e.g., using controller processor 359, memory 360, etc.).

Implementation examples are described in the following numbered clauses:

1. a method of wireless communication by a sidelink UE (user equipment), comprising:

receiving a first signal at a beginning of a sidelink DRX on duration as part of a Discontinuous Reception (DRX) wake-up procedure;

sending a response to the first signal as part of a DRX wakeup process;

starting a timer after sending the response; and

entering a sleep state when a physical sidelink channel is not received before the timer expires.

2. The method of clause 1, further comprising:

receiving the physical sidelink channel before the timer expires; and

in response to receiving the physical sidelink channel, a sidelink inactivity timer is started.

3. The method of clause 2, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are preconfigured for each link, for each link type, for each traffic type, or for each UE.

4. The method of clause 1, wherein the sidelink DRX cycle startoffset and sidelink DRX on duration timers are set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

5. The method of clause 1, wherein a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured for each link, for each link type, for each traffic type, or for each UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

6. The method of clause 1, further comprising: remains awake during the random access procedure until the last random access message is transmitted or received.

7. The method of clause 1, wherein no preconfigured physical sidelink channel resource coincides with a duration of a respective timer, the method further comprising: sleep during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

8. The method of clause 1, wherein the sidelink DRX cycle setting is the same for communication with each of the plurality of transmitting UEs.

9. The method of clause 1, wherein the sidelink DRX on duration timer is started after DRX-SlotOffset from the beginning of a subframe, wherein the subframe is such that for a long DRX cycle, [ (subframe number (SFN) × 10) + subframe number ] modulo (DRX-LongCycle) = DRX-StartOffset, and for a short DRX cycle (if configured), [ (SFN × 10) + subframe number ] modulo (DRX-ShortCycle) = (DRX-StartOffset) modulo (DRX-ShortCycle);

a sidelink inactive Transmit (TX) timer is started at the transmission of the physical sidelink channel;

a sidelink inactivity Receive (RX) timer is started at reception of the physical sidelink channel;

a sidelink DRX HARQ RTT TX timer is started at the transmission of the physical sidelink channel;

a sidelink DRX HARQ RTT RX timer starts at the transmission of a Negative Acknowledgement (NACK) on a received physical sidelink channel;

a sidelink DRX retransmission TX timer is started when the sidelink DRX HARQ RTT TX timer expires; and

a sidelink DRX retransmission RX timer is started upon the expiration of the sidelink DRX HARQ RTT RX timer.

10. The method of clause 1, wherein the physical sidelink channel comprises a Physical Sidelink Control Channel (PSCCH).

11. The method of clause 1, wherein the physical sidelink channel comprises a Physical Sidelink Shared Channel (PSSCH).

12. A Sidelink (SL) UE (user equipment) for wireless communication, comprising:

a memory; and

at least one processor operably coupled to the memory, the memory and the at least one processor configured to:

sending a response to the first signal as part of a DRX wakeup process;

starting a timer after sending the response; and

13. The UE of clause 12, wherein the at least one processor is further configured to:

receiving the physical sidelink channel before the timer expires; and

14. The UE of clause 13, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are preconfigured for each link, for each link type, for each traffic type, or for each UE.

15. The UE of clause 12, wherein the sidelink DRX cycle startoffset and sidelink DRX on duration timers are set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

16. The UE of clause 12, wherein a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured per link, per link type, per traffic type, or per UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

17. The UE of clause 12, wherein the at least one processor is further configured to: remains awake during the random access procedure until the last random access message is transmitted or received.

18. The UE of clause 12, wherein no preconfigured physical sidelink channel resources are consistent with the duration of the respective timer, the at least one processor further configured to: sleep during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

19. The UE of clause 12, wherein the sidelink DRX cycle setting is the same for communication with each of the plurality of transmitting UEs.

20. The UE of clause 12, wherein the sidelink DRX on duration timer is started after DRX-SlotOffset from a beginning of a subframe, wherein the subframe is such that for long DRX cycles, [ (subframe number (SFN) × 10) + subframe number ] modulo (DRX-LongCycle) = DRX-StartOffset, and for short DRX cycles, (if configured), [ (SFN × 10) + subframe number ] modulo (DRX-ShortCycle) = (DRX-StartOffset) modulo (DRX-ShortCycle);

21. The UE of clause 12, wherein the physical sidelink channel comprises a Physical Sidelink Control Channel (PSCCH).

22. The UE of clause 12, wherein the physical sidelink channel comprises a physical sidelink shared channel (psch).

23. A Sidelink (SL) UE (user equipment) for wireless communication, comprising:

means for receiving a first signal at a beginning of a sidelink DRX on duration as part of a Discontinuous Reception (DRX) wake-up procedure;

means for transmitting a response to the first signal as part of a DRX wake-up procedure;

means for starting a timer after sending the response; and

means for entering a sleep state when a physical sidelink channel is not received before the timer expires.

24. The UE of clause 23, further comprising:

means for receiving the physical sidelink channel before the timer expires; and

means for starting a sidelink inactivity timer in response to receiving the physical sidelink channel.

25. The UE of clause 24, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are preconfigured per link, per link type, per traffic type, or per UE.

26. The UE of clause 23, wherein the sidelink DRX CycleStartOffset and sidelink DRX on duration timers are set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

27. The UE of clause 23, wherein a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured per link, per link type, per traffic type, or per UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

28. The UE of clause 23, further comprising: means for remaining awake during a random access procedure until a last random access message is transmitted or received.

29. The UE of clause 23, wherein no preconfigured physical sidelink channel resources coincide with the duration of the respective timer, further comprising: means for sleeping during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

30. The UE of clause 23, wherein the sidelink DRX cycle setting is the same for communication with each of the plurality of transmitting UEs.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit aspects to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of various aspects.

As used, the term "component" is intended to be broadly interpreted as hardware, firmware, and/or a combination of hardware and software. As used, a processor is implemented in hardware, firmware, and/or a combination of hardware and software.

Some aspects are described in connection with a threshold. As used, meeting a threshold may refer to a value greater than a threshold, greater than or equal to a threshold, less than or equal to a threshold, not equal to a threshold, and the like, depending on the context.

It will be apparent that the described systems and/or methods may be implemented in different forms of hardware, firmware, and/or combinations of hardware and software. The actual specialized control hardware or software code used to implement the systems and/or methods is not limiting in every respect. Thus, the operation and behavior of the systems and/or methods were described without reference to the specific software code-it being understood that software and hardware may be designed to implement the systems and/or methods based, at least in part, on the description.

Even if specific combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the various aspects. Indeed, many of these features may be combined in ways not specifically recited in the claims and/or specifically disclosed in the specification. While each dependent claim listed below may depend directly on only one claim, the disclosure of the various aspects includes a combination of each dependent claim with every other claim in the set of claims. A phrase referring to "at least one of a list of items" refers to any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to encompass any combination of a, b, c, a-b, a-c, b-c, and a-b-c, as well as multiples of the same element (e.g., any other ordering of a, b, and c), such as a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b-b, b-b-c, c-c, and c-c-c, or a, b, and c).

No element, act, or instruction used should be construed as critical or essential unless explicitly described as such. In addition, as used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more". Further, as used, the terms "set" and "group" are intended to include one or more items (e.g., related items, unrelated items, combinations of related items and unrelated items, etc.) and may be used interchangeably with "one or more. Where only one item is intended, the phrase "only one" or similar language is used. Further, as used, the terms "having," "having," and/or the like are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise.

Claims

sending a response to the first signal as part of a DRX wakeup process;

starting a timer after sending the response; and

2. The method of claim 1, further comprising:

receiving the physical sidelink channel before the timer expires; and

3. The method of claim 2, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are pre-configured for each link, for each link type, for each traffic type, or for each UE.

4. The method of claim 1, wherein a sidelink DRX cycle startoffset and sidelink DRX on duration timer is set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

5. The method of claim 1, in which a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured per link, per link type, per traffic type, or per UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

6. The method of claim 1, further comprising: remains awake during the random access procedure until the last random access message is sent or received.

7. The method of claim 1, wherein no preconfigured physical sidelink channel resource coincides with a duration of a respective timer, the method further comprising: sleep during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

8. The method of claim 1, wherein the sidelink DRX cycle setting is the same for communication with each of the plurality of transmitting UEs.

9. The method of claim 1 wherein the sidelink DRX on duration timer is started after DRX-SlotOffset from the beginning of a subframe, wherein the subframe is such that for long DRX cycles, [ (subframe number (SFN) × 10) + subframe number ] modulo (DRX-LongCycle) = DRX-StartOffset, and for short DRX cycles (if configured), [ (SFN × 10) + subframe number ] modulo (DRX-ShortCycle) = (DRX-StartOffset) modulo (DRX-ShortCycle);

a sidelink DRX HARQ RTT RX timer is started at the transmission of a Negative Acknowledgement (NACK) on a received physical sidelink channel;

10. The method of claim 1, wherein the physical sidelink channel comprises a Physical Sidelink Control Channel (PSCCH).

11. The method of claim 1, wherein the physical sidelink channel comprises a Physical Sidelink Shared Channel (PSSCH).

12. A Sidelink (SL) UE (user equipment) for wireless communication, comprising:

a memory; and

sending a response to the first signal as part of a DRX wakeup process;

starting a timer after sending the response; and

13. The UE of claim 12, wherein the at least one processor is further configured to:

receiving the physical sidelink channel before the timer expires; and

14. The UE of claim 13, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are pre-configured for each link, for each link type, for each traffic type, or for each UE.

15. The UE of claim 12, wherein the sidelink DRX cycle startoffset and sidelink DRX on duration timers are set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

16. The UE of claim 12, wherein a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured per link, per link type, per traffic type, or per UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

17. The UE of claim 12, wherein the at least one processor is further configured to: remains awake during the random access procedure until the last random access message is transmitted or received.

18. The UE of claim 12, wherein no preconfigured physical sidelink channel resource coincides with a duration of a respective timer, the at least one processor further configured to: sleep during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

19. The UE of claim 12, wherein the sidelink DRX cycle setting is the same for communications with each of the plurality of transmitting UEs.

20. The UE of claim 12 wherein the sidelink DRX on duration timer is started after DRX-SlotOffset from the beginning of a subframe, wherein the subframe is such that for long DRX cycles, [ (subframe number (SFN) × 10) + subframe number ] modulo (DRX-LongCycle) = DRX-StartOffset, and for short DRX cycles (if configured), [ (SFN × 10) + subframe number ] modulo (DRX-ShortCycle) = (DRX-StartOffset) modulo (DRX-ShortCycle);

21. The UE of claim 12, wherein the physical sidelink channel comprises a Physical Sidelink Control Channel (PSCCH).

22. The UE of claim 12, wherein the physical side uplink channel comprises a physical side uplink shared channel (psch).

23. A Sidelink (SL) UE (user equipment) for wireless communication, comprising:

means for starting a timer after sending the response; and

24. The UE of claim 23, further comprising:

means for receiving the physical sidelink channel before the timer expires; and

25. The UE of claim 24, wherein the sidelink inactivity timer, sidelink DRX on duration timer, and sidelink DRX retransmission timer are pre-configured for each link, for each link type, for each traffic type, or for each UE.

26. The UE of claim 23, wherein the sidelink DRX CycleStartOffset and sidelink DRX on duration timers are set such that each sidelink DRX on duration coincides with at least one pre-configured physical sidelink channel resource.

27. The UE of claim 23, wherein a minimum value of a sidelink DRX hybrid automatic repeat request (HARQ) Round Trip Time (RTT) timer is preconfigured per link, per link type, per traffic type, or per UE, and an actual value of the sidelink DRX HARQ RTT timer is dynamically adjusted to ensure that at least one physical sidelink channel resource coincides with a duration of an input sidelink DRX retransmission timer.

28. The UE of claim 23, further comprising: means for remaining awake during a random access procedure until a last random access message is transmitted or received.

29. The UE of claim 23, wherein no preconfigured physical sidelink channel resources coincide with a duration of a respective timer, the UE further comprising: means for sleeping during an inactivity timer, a sidelink DRX on duration timer, or a sidelink DRX retransmission timer.

30. The UE of claim 23, wherein the sidelink DRX cycle setting is the same for communication with each of the plurality of transmitting UEs.